Hybridization 103 



are better known than in any other American plants. 

 The great genus Carex, or sedge, which occurs in great 

 numbers and many species in almost every locality in 

 the United States, and in which the species are particularly 

 adapted to inter-crossing by the character of their in- 

 florescence, furnishes but few undoubted hybrids. Among 

 one hundred and eighty-five species and .prominent 

 varieties inhabiting the Northeastern States, there are 

 only about a score of hybrids recorded, and all of them are 

 rare or local, some of them having been collected but 

 once. Species of Carex of remarkable similarity may 

 grow side by side for years, even inter-tangled in the 

 same clump, and yet produce no hybrid. These examples 

 show that nature avoids hybridization, a conclusion at 

 which we have already arrived from philosophical con- 

 siderations. And we have reason to infer the same 

 conclusion from the fact that flowers of different species 

 are so constructed as not to invite inter-crossing. But, 

 on the other hand, the fact that all higher plants habitually 

 propagate by means of seeds, which is far the most ex- 

 pensive to the plant of all methods -of propagation, while 

 at the same time most flowers are so constructed as to 

 prevent self-fertilization, shows that some corresponding 

 good must come from crossing within the limits of the 

 species or variety ; and there are also philosophical reasons, 

 as we have seen, that warrant this conclusion. 



Change of seed and crossing. Bearing in mind these 

 good influences of crossing, let us recall another series 

 of facts following the simple change of seed. Almost 

 every farmer and gardener at the present day feels that 

 an occasional change of seed results in better crops, and 



